The development of a high performance optical modulator is essential for silicon photonics integrated circuits. A possible approach is the hybrid integration of conventional III-V semiconductor or lithium niobate modulators onto a silicon platform. However, this approach does not leverage on the existing complementary metal-oxide-semiconductor (CMOS) process technology to enable low costs and high volume manufacturability of electronic-photonic integrated circuits.
A silicon-based modulator may be more attractive as it may allow the monolithic integration of photonic components with silicon CMOS on a single chip. Silicon-based modulators which use the free carrier plasma dispersion effect for modulation have been demonstrated. The silicon Mach-Zehnder interferometer (MZI) modulator is one such example. However, its long phase shifter length may result in high energy consumption and large on-chip area. A silicon micro-ring resonator modulator may eliminate this issue due to its smaller size, but it may be more susceptible to fabrication errors and has a smaller modulation bandwidth.